Owncloud - user_ldap fails while upgrading to 7.0.1

[Paul Muster <paul@muster.net>]

Hello there,

after upgrading Owncloud from 6.0.3+dfsg-2~bpo70+1 to 
7.0.1+dfsg-1~bpo70+1 and pressing "Start update" I get this error:

An exception occurred while executing 'ALTER TABLE 
`oc_oc_ldap_user_mapping_765af71f2a59b` DROP PRIMARY KEY': 
SQLSTATE[42000]: Syntax error or access violation: 1091 Can't DROP 
'PRIMARY'; check that column/key exists

What happened? How to fix it?

Which information can I deliver to enable you analyzing this?

Is this a Backports-specific problem or should it better be discussed on 
a) the Debian bug tracking system or b) the normal owncloud-user 
mailinglist?

Thanks & greetings,

Paul